Lecture 5 medium

Questions and Answers

What is one of the primary functions of the smooth ER in the liver?

Production of ribosomes

Regulation of calcium ion concentrations

Synthesis and storage of enzymes for detoxification (correct)

Storage of glycogen

Which type of cell contains a specific version of the smooth ER known as the sarcoplasmic reticulum?

Muscle cells (correct)

Nerve cells

Liver cells

Adrenal gland cells

How does the smooth ER primarily differ from the rough ER?

Presence of ribosomes

Complexity of its structure (correct)

Function in protein synthesis

Location within the cell

What substance does the smooth ER in adrenal glands secrete as a precursor to steroid hormones?

Cholesterol Signup and view all the answers

Which of the following substances does the smooth ER help metabolize?

Exogenous drugs and toxins Signup and view all the answers

What is the primary function of lysosomes in autophagy?

Digestion of unnecessary or damaged cell parts Signup and view all the answers

Where do primary lysosomes originate from?

Golgi apparatus Signup and view all the answers

What happens during heterophagia?

Breakdown of foreign substances absorbed through endocytosis Signup and view all the answers

Which of the following best describes autolysis?

Breakdown of cells due to pathology or aging Signup and view all the answers

What is the fate of indigestible molecules in secondary lysosomes?

Released as residual bodies Signup and view all the answers

How do secondary lysosomes differ from primary lysosomes?

They merge with endocytosed vesicles and are involved in digestion Signup and view all the answers

What is the primary function of the endoplasmic reticulum?

Production and processing of proteins Signup and view all the answers

Which statement accurately describes the structural features of the endoplasmic reticulum?

It is composed of rough sheets and smooth tubules. Signup and view all the answers

What distinguishes the rough endoplasmic reticulum from the smooth endoplasmic reticulum?

Rough ER has ribosomes attached to its membranes. Signup and view all the answers

Why is the endoplasmic reticulum considered essential for protein synthesis?

It is the site of translation for mRNA into proteins. Signup and view all the answers

What role does the endoplasmic reticulum play regarding calcium ions?

It serves as a storage site for calcium ions. Signup and view all the answers

What happens to proteins synthesized in the rough endoplasmic reticulum?

They can be modified and transported to various cell destinations. Signup and view all the answers

What structural feature allows the endoplasmic reticulum to maintain its shape?

Interconnected network held by the cytoskeleton. Signup and view all the answers

What is the primary function of lysosomes in a cell?

Waste breakdown Signup and view all the answers

Which process involves the breakdown of damaged cellular components by lysosomes?

Autophagy Signup and view all the answers

What happens during cellular repair involving lysosomes?

Lysosomes break down harmful materials Signup and view all the answers

What can occur when a cell is damaged beyond repair, involving lysosomes?

Autolysis Signup and view all the answers

Which of the following best describes what lysosomes recycle?

Broken down molecules into new cellular products Signup and view all the answers

What distinguishes the cis Golgi network from the trans Golgi network?

The cis network is closer to the ER than the trans network. Signup and view all the answers

Which of the following do lysosomes help to regulate in a cell?

Immune response Signup and view all the answers

Which structure in the Golgi contains enzymes crucial for modifying proteins?

Lumen Signup and view all the answers

What type of vesicles carry cargo away from the Golgi after processing?

Secretory vesicles Signup and view all the answers

In what way do lysosomes contribute to cellular homeostasis?

By breaking down excess cellular material Signup and view all the answers

What is the primary function of the Golgi apparatus?

To transport, modify, and package proteins and lipids. Signup and view all the answers

Which type of material is NOT typically broken down by lysosomes?

Water molecules Signup and view all the answers

Where do incoming vesicles originate before they reach the Golgi?

Endoplasmic Reticulum Signup and view all the answers

What additional complex molecules can be created in the Golgi besides proteins and lipids?

Complex polysaccharides Signup and view all the answers

What role do vesicles play in the Golgi network?

They transport proteins, lipids, and other cargo. Signup and view all the answers

What happens to vesicles containing processed material from the Golgi?

They travel to lysosomes or the plasma membrane. Signup and view all the answers

The lumen of the Golgi is best described as?

The internal cavity of the cisternae. Signup and view all the answers

What is the primary function of lysosomes within a cell?

Waste degradation and recycling Signup and view all the answers

Where are lysosomes primarily formed?

Golgi apparatus Signup and view all the answers

What type of environment do the hydrolytic enzymes within lysosomes require to work optimally?

Acidic pH of 4.5 to 5.5 Signup and view all the answers

What is the process called that allows external materials to enter the cell for degradation?

Endocytosis Signup and view all the answers

How many different acid hydrolases are typically found in lysosomes?

60 Signup and view all the answers

What initiates the intake process of vesicles by lysosomes?

Signaling proteins on the lysosomal membrane Signup and view all the answers

What happens after a vesicle fuses with a lysosome?

Materials inside the vesicle are digested Signup and view all the answers

Which cellular structure is involved in the initial synthesis of enzymes that become lysosomal hydrolases?

Rough endoplasmic reticulum Signup and view all the answers

Which of the following does NOT correctly describe lysosomes?

They are formed in the nucleus. Signup and view all the answers

What role do hydrolytic enzymes play within lysosomes?

Dissolve molecules Signup and view all the answers

Study Notes

Smooth ER

Located near the cell periphery, the smooth endoplasmic reticulum (SER) lacks ribosomes, distinguishing it from rough ER.
Functions include lipid, steroid, and carbohydrate synthesis, along with metabolizing drugs and toxins.
The type of cell influences the specific functions of the SER.
In muscle cells, it's known as the sarcoplasmic reticulum, regulating calcium ion concentrations during muscle contraction and relaxation.
In adrenal glands, SER secretes cholesterol, a precursor to steroid hormones.
In liver cells, SER synthesizes and stores detoxifying enzymes to process harmful substances like alcohol and drugs.

Functions of ER

Rough ER (RER) is primarily responsible for protein production, while SER synthesizes phospholipids and steroids.
The ER detoxifies harmful exogenous molecules and regulates calcium ion sequestration and release.

Lysosomes

Heterophagia involves breaking down foreign substances absorbed via endocytosis.
Autophagy is the process of degrading internal materials, including nutrients and dysfunctional organelles.
Autolysis occurs when lysosomes rupture, digesting the cell due to pathology or aging.
Primary lysosomes form from the Golgi apparatus and contain inactive hydrolases for degrading large molecules.
Secondary lysosomes form when primary lysosomes merge with endocytic vesicles, digesting various materials and recycling products to the cytoplasm.

Endoplasmic Reticulum Structure and Function

The endoplasmic reticulum (ER) produces, processes, and secretes proteins, playing a vital role in every cell of humans and other organisms.
Its structure consists of interconnected flattened sheets (cisternae) and tubules, facilitating efficient function.
Rough ER is studded with ribosomes, while the smooth ER lacks them.

Rough ER

Lumen of rough ER is narrower than that of smooth ER.
Central to protein synthesis as ribosomes translate mRNA into proteins, which are then modified and transported.

Golgi Network

Composed of two networks: cis and trans Golgi networks, each made of multiple cisternae.
The cis Golgi network is adjacent to the ER, while the trans Golgi network is the farthest.
The Golgi modifies proteins and lipids received from the ER, packaging them into vesicles for transport.

Protein Trafficking

Newly synthesized proteins are transported from the ER to the Golgi for modification and sorting to their destinations.
The Golgi creates polysaccharides and packages proteins and lipids within vesicles for secretion or internal use.

Lysosome Functionality

Lysosomes are membrane-bound organelles responsible for cellular waste degradation and recycling.
Their acidic internal environment (pH 4.5-5.5) contains hydrolytic enzymes, facilitating the breakdown of internal and external materials.
They play a role in autophagy, cellular repair, and can trigger autolysis when a cell is irreparably damaged.

Ribosome Structure and Function

Ribosomes are essential for protein synthesis, directing what type of proteins are produced based on location.
Composed of two subunits (large and small), they come together to facilitate protein production when needed.
The ribosomal process involves initiation, elongation, and termination of protein synthesis.

Golgi Apparatus Structure

The Golgi apparatus, made up of stacked pouches called cisternae, operates closely with the ER.
Composed of the cis face (closest to the ER), trans face (farthest from the ER), and medial section, it processes proteins and lipids.
The endoplasmic reticulum-Golgi intermediate compartment (ERGIC) facilitates transport between the ER and Golgi.

Golgi Processing Steps

Proteins or lipids leave the ER as vesicles, enter the Golgi at the cis face, and are modified as they move through its lumen.
Modifications may include sugar replacements or the addition of fatty acids or phosphates.
At the trans face, molecules are sorted and packaged into vesicles for delivery to specific cellular locations.

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Description

This quiz explores the functions and structures of the smooth and rough endoplasmic reticulum (ER), highlighting their roles in lipid and protein synthesis, detoxification, and cellular regulation. Understand how these organelles differ in various cell types, including muscle and liver cells, and learn about lysosomal functions related to autophagy and heterophagy.